A. Field of the Invention
The present invention relates to duct work used to convey air for heating, ventilating or air conditioning commercial, industrial and residential buildings. More particularly, the invention relates to a method and apparatus for making self-gripping air vanes provided with button-like protuberances which adapt the vanes to be lockingly fastenable to a pair of opposed air turning rails without tools to form a complete air turning assembly.
B. Description of Background Art
Flowing air used to ventilate, heat, or cool buildings is typically routed through a network of interconnected, elongated, straight rectangular cross-section tubes or ducts, which are collectively referred to as duct work. Changes in the orientation or directional bearing of ducts is usually effected by coupling a pair of ducts together with an angled transition section or elbow. These are bent at an angle, typically of 90 degrees, and have rectangular or circular openings for attachment to separate ducts oriented at the particular bend angle with respect to one another.
When air flowing through a duct impacts the side wall of an elbow or transition section disposed perpendicularly to the flow direction, substantial turbulence is created in the flowing air mass, even when the flow velocity is relatively modest. This turbulence impedes air flow, causing an increase in static pressure and pressure loss coefficients, thus necessitating the use of larger blowers that consume increased drive power, to maintain a given air flow rate at the outlet of the elbow section. Moreover, undesirable vibration and noise may be generated within the duct work, if the turbulence is sufficiently great.
For the reasons stated above, ventilation elbows or transition sections are often constructed to include means for minimizing turbulence, usually by encouraging laminar flow within the elbow. Thus, ventilation elbows constructed to minimize turbulence typically employ a plurality of curved, parallel blades or turning vanes spaced apart at regular intervals, to promote laminar air flow where the direction of air flow changes within the elbow. Typical turning vane assemblies use a plurality of curved sheet metal vanes disposed between a pair of flat, parallel metal sheets, often referred to as rails. The assembly is secured within an angled transition section or elbow.
Turning vane assemblies which employ a variety of techniques for fastening turning vanes to rails has been disclosed in the following United States patents:
Steffens, U.S. Pat. No. 2,292,246, Aug. 4, 1942, Duct Turn: Discloses curved double wall non-metallic duct turns or vanes having a metal insert with a tab that fits into slots cut longitudinally inward from the diagonal end wall of a duct shell, the tab having a protruding finger which is bent flush with the diagonal end wall.
Speiser, U.S. Pat. No. 2,826,221, Mar. 11, 1958, Duct Devices: Discloses duct devices that utilize vanes in the shape of a rectangular plate curved to form a partition wall or guide plate having parallel top and bottom horizontal edges and parallel vertical side edges. Both the top edge and bottom edge of each vane have formed therein a pair of vertically disposed cuts, forming at each cut two tongues, for a total of four tabs. This vane construction requires the provision in each plate or rail of a pair of longitudinally disposed channels or grooves having a V-shaped transverse cross-section. The grooves are formed by downwardly converging walls intersecting on fold line. Each groove or channel has formed therein a plurality of longitudinally spaced apart obliquely disposed slots to receive a pair of tongues, which must be peened over in opposite directions flush with the bottom walls of the V-shaped groove to retain a vane in position between the rails.
Gracer, U.S. Pat. No. 2,861,597, Nov. 25, 1958, Air Guide Device: Discloses single and double wall turning vanes secured in slots formed in the bottoms of dimples protruding inward from rails, by deforming lateral edge walls of the vanes protruding outwards through the slots.
Perlin, U.S. Pat. No. 2,884,956, May 5, 1959, Air Guide Device: Discloses flanged, slotted cup-shaped members inserted through holes formed in a pair of opposed side plates, to secure between the side plates turning blades positioned in the slots.
Gracer, U.S. Pat. No. 2,959,195, Nov. 8, 1960, Air Guide Device: Discloses an air turning assembly having a plurality of curved, rectangular plan view turning vanes or blades that are secured to a pair of rails by crimping opposite lateral edges of the blades protruding outwards through slots in inwardly extending protuberances formed in the rails.
Chesser, U.S. Pat. No. 3,050,160, Aug. 21, 1962, Sheet Metal Connection And Method For Effecting Same: Discloses a sheet metal connection employing a tongue protruding perpendicularly from a first plate inserted through a slot in a second plate, deformations being formed outwards from the plane of the tongue to lock it in place relative to the second plate.
Noll, U.S. Pat. No. 3,075,450, Jan. 29, 1963, Cap Assembly: Discloses a hollow tubular cap assembly having the shape of the frustrum of a cone, connectable to a cylindrical tube by extending flexible straps.
Bohannon, U.S. Pat. No. 3,144,204, Aug. 11, 1964, Centrifugal Blower Wheel: Discloses a centrifugal blower wheel having double-wall, air-foil shaped blades having a plurality of tabs protruding from opposite straight side walls thereof, the tabs on the two walls of each blade being inserted into first and second groups of slots provided through front and rear circular end plates, and bent over to retain the blades in place.
Olmsted, et al., U.S. Pat. No. 3,224,668, Dec. 21, 1965, Blower Wheel Wedged End Blade Mounting: Discloses curved blower wheel blades attachable to annular side rings by a central finger or tongue protruding from opposite short lateral edges of the blade. The fingers are bent into a V-shape, inserted into semi-circular or triangular-shaped holes through the side rings, and bent over to retain the blades in the rings.
Jacobsen, U.S. Pat. No. 3,381,713, May 7, 1968, Turning Vane And Rail Construction: Discloses double-wall, airfoil-shaped turning vanes having formed in the inner side of one wall a pair of cylindrically-shaped passageways disposed perpendicularly inwards from the outer lateral edge of the wall. Headed pins or nails are driven through holes provided in a pair of parallel side rails into the passageways, to secure the vanes to the rails.
Harper, U.S. Pat. No. 3,405,737, Oct. 15, 1968, Duct Device: Discloses double wall vanes secured in slots cut in inwardly protruding depressions in opposed side rails.
Hinden, U.S. Pat. No. 3,494,379, Feb. 10, 1970, Air Turning Assembly And Mounting Rail: Discloses an air turning assembly which employs turning vanes formed of glass fiber impregnated with a polymer and inserted through curved apertures or sockets punched in U-cross section rails. The sockets are outlined by outwardly deflected, spaced tabs or shoulder portions which are compressed by a cam lock against the protruding portion of a vane, thereby securing the vane to the rail.
Hinden, U.S. Pat. No. 3,602,262, Aug. 31, 1971, Air Turning Assembly: Discloses an air turning assembly utilizing fibrous, compressible vane members secured to a pair of parallel rails between the sides of a U-shaped clamp protruding inward from a rail and secured thereto.
Myers, U.S. Pat. No. 4,467,829, Aug. 28, 1984, Turning Vane Rail: Discloses a rail for mounting sheet metal turning vanes that includes a sheet and integral vane guides extending generally perpendicularly away from the plane of the sheet. Each vane guide is a plate slit from the sheet except for one edge along which the plate is bent. The plate is adapted to be positioned adjacent to a wall of the vane. An access aperture, partially located in the sheet and partially located in the plate is adapted to allow access to a portion of the vane wall for contact by a striking tool. A blow from the tool splits the sheet metal vane wall to form tabs which are folded through the aperture, which securely attaches the wall to the rail.
DeLord, U.S. Pat. No. 4,641,684, Feb. 10, 1987, Rail For An Air Turning Vane Assembly: Discloses an air turning vane assembly in which the vanes are attached to tabs formed in each rail by integral locking clips formed upon the rail tabs. The rail assembly is constructed from rails having cutout portions adapted to receive the tabs of similar rails, to permit compact nesting for storage and shipping. The assembly requires use of a special locking tool that has a cutting tooth which cuts a ribbon in a vane wall to form an integral locking clip for securing the vanes to rails.
Myers, U.S. Pat. No. 4,911,205, Mar. 27, 1990, Apparatus And Method For Duct Vane Mounting: Discloses a duct vane assembly having rails in which a pair of inwardly projecting, rectangular tabs lying in an arc are formed. Each tab is insertably secured in a laterally disposed slot formed near the outer lateral edge of each curved turning vane, the slot being defined by a lateral strap formed in the vane adjacent its end. A finger bent in the end of a rail tab projects into an opening in the vane adjacent the strap to positively retain the vane connected to the rails.
Felson, U.S. Pat. No. 5,068,957, Dec. 3, 1991, Turning Vane Setting Tool: Discloses a device and method for permanently anchoring air turning vanes to manufactured vane rails or runners in duct work systems that utilizes pre-positioning, splitting and bending means combined into one continuous sequence when the tool is applied to the exposed edge of an air turning vane which has been inserted into the slotted depression of manufactured vane rails or runners and is activated by means of a hammer blow or similar energy source.
Lyons, et al., U.S. Pat. No. 5,181,314, Jan. 26, 1993, Apparatus For Manufacturing Air Turning Assembly: Discloses an apparatus and method for forming air turning assemblies. The vanes are conventional bowed rectangular sheets, the lateral edges of which are secured in slotted projections on the inner surface of each rail by chisel lips entering the slots in projections and bending over the edges of the vane protruding therethrough.
The Gracer, Felson and Lyons, et al. patents all disclose a turning vane and rail construction which requires the formation of slotted depressions in the rails to secure the vanes thereto. The Hinden ""379 patent discloses a turning vane assembly which uses tabs projecting outward from the perimeter of an aperture through a flat rail which are compressed by a locking cam against the perimeter of a compressible vane protruding through the aperture. The Hinden ""262 patent discloses the use of a U-shaped compression bracket protruding inwards from a rail and attached thereto by a pop rivet to compress the end of a resilient vane, to which it is secured by another pop rivet. DeLord discloses a rail for a turning vane assembly that utilizes tabs bent inwards from apertures in the rail to attach to an integral locking clip formed in the end wall of a vane by a special tool. Myers discloses a vane and rail construction which utilizes a strap formed near each end of a vane by a laterally disposed slot, the slot insertably receiving a tab bent out from an aperture formed in a rail and secured to the vane by a finger bent out from the end of the tab.
Vane and rail assemblies known to the present inventors, including those cited above, generally require that portions of sheet metal vanes or rails which are to be joined together be deformed by robustly pounding parts thereof, using either a hammer, chisel, or specially designed tools, to fasten the vanes and rails together. Sometimes, pounding on a vane and rail assembly to install a series of vanes can loosen the fastening of vanes installed earlier. Then, when a completed vane and rail assembly has been installed into a duct work elbow; and the latter installed in a building, variations in the pressure of air flowing through the duct work can cause the xe2x80x9ccheeksxe2x80x9d or walls of curved transition sections to expand and contract, and perpendicular duct walls to flex inward and outward or xe2x80x9coil-canxe2x80x9d in response to air pressure fluctuations. Since environmental control systems for buildings require that air flow be turned on and off intermittently, or varied by control dampers, duct work air turning vane assemblies are routinely subjected to such wall deformations. As a result, vanes which had been initially loosened during the fabrication of a turning vane and rail assembly can become completely detached from the rails long after duct work has been installed in a building. As can be readily appreciated, replacing dislodged turning vanes can be an extremely time consuming, laborious and expensive process, particularly in high-rise buildings.
Partly in response to limitations of prior art air turning vane and rail assemblies, the present inventors developed improved air turning vane and rail assemblies of simplified construction and greater versatility than existing assemblies, in which vanes self-lock into engagement with rails, thereby minimizing the likelihood of vanes dislodging from a vane and rail assembly. Those improved turning vane and rail assemblies are disclosed in the present inventors"" co-pending application Ser. No. 08/912,385, filed Aug. 18, 1997. The disclosure of this application is hereby incorporated by reference into the present disclosure.
An embodiment of an air turning vane and rail assembly according to the co-pending disclosure includes a pair of laterally spaced apart parallel rails. Each of the rails has a plurality of longitudinally spaced apart, generally trapezoidally-shaped tabs, each bent perpendicularly inwardly towards the opposite rail from a separate perforation through the rail. Each of the upstanding tabs has through its thickness an aperture located near the base of the tab. A plurality of self-gripping double air-foil vanes lockingly engage the tabs, each vane having a generally hemispherically shaped protuberance which protrudes forward through the aperture from a rear concave air-foil plate towards a front convex airfoil plate. In this embodiment the protuberance has an inner flat, transversely disposed lip which locks against the upper wall of the aperture through the tab, when the tab is forcibly inserted into the opening between the front and rear airfoil plates of a vane.
The present invention was conceived of to provide a novel and advantageous method and apparatus for forming self-locking protuberances in air turning vanes of the type described above.
An object of the present invention is to provide a method for forming a locking button in a double airfoil air turning vane, the locking button being adapted to lockingly engage the edge wall of an aperture provided through a tab upstanding from an air turning rail.
Another object of the invention is to provide a method for forming in an airfoil plate of an air turning vane a generally hemispherically-shaped protuberance which may be used to lockingly engage an air turning rail.
Another object of the invention is to provide a method for forming in an airfoil plate of a double-airfoil air turning vane a locking button which protrudes inwards towards the other airfoil plate.
Another object of the invention is to provide a method for severing from a length of double airfoil plate air turning vane stock an air turning vane of a desired length, while simultaneously forming in one of said airfoil plates a generally hemispherically-shaped protuberance which may serve as a locking button for subsequent attachment of the air turning vane to a rail.
Another object of the invention is to provide a method for severing from a length of double airfoil plate air turning vane stock an air turning vane of a desired length, while simultaneously forming in an airfoil plate near the transverse severed edge of the vane and near the transverse severed edge of the vane stock separate locking buttons which protrude forward towards the other airfoil plate.
Another object of the invention is to provide an apparatus for receiving a length of double airfoil vane stock, severing from the vane stock a double plate air turning vane of a desired length, and forming in a first airfoil plate of the severed air turning vane a button-like locking protuberance located proximate the severed edge of the turning vane.
Another object of the invention is to provide an apparatus for receiving a length of double airfoil plate air turning vane stock, severing from the vane stock a double airfoil plate air turning vane of a desired length and forming in a first airfoil plate portion of both the severed air turning vane and the air turning vane stock a button-like locking protuberance located inwards from the respective severed edges of the air turning vane and the stock from which it was severed.
Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.
It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, we do not intend that the scope of our exclusive rights and privileges in the invention be limited to details of the embodiments described. We do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.
The present inventors"" application Ser. No. 08/912,385 now U.S. Pat. No. 5,927,339 issued Jul. 27, 1999, discloses improved air turning vane and rail assemblies for promoting laminar air flow at locations within heating, ventilating or air conditioning (xe2x80x9cHVACxe2x80x9d) duct work where the air flow direction must change, as for example, within an elbow bent at 90 degrees or other angle. The present invention comprehends an apparatus and methods for making self-gripping air turning vanes of the type disclosed in the 339 patent.
According to the disclosure of present inventors"" b 339 patent, an improved turning vane and rail assembly for promoting laminar air flow was described, in which vanes may be fastened to rails without requiring the use of tools. Thus, vane and rail air turning assemblies according to the 339 patent may be readily assembled at job sites from compact packages of rails and vanes.
Preferred embodiments of an improved air turning vane and rail assembly according to applicants"" prior invention disclosed in the xe2x80x9c339xe2x80x9d patent utilize double-plate, airfoil-type turning vanes. According to the disclosure of prior disclosed invention, the turning vane has an arcuately curved, convex front airfoil plate joined at opposite longitudinal edge walls thereof to a concave rear airfoil plate having less curvature, i.e., a larger radius of curvature than the front plate.
Air turning vanes thus described are attached to a pair of flat elongated rectangular sheet metal rails, perpendicularly disposed between the rails, in a novel construction in which each of the two rails of an air turning assembly comprises an elongated rectangular strip of sheet metal in which a plurality of generally polygonally-shaped perforations have been made at regular longitudinal intervals along the strip. Each perforation has a modified trapezoidal shape, defined by a laterally symmetric, wedge-shaped trapezoidal upper portion, and a laterally elongated, rectangular portion pedestal. The base of the rectangular lower portion of the perforation is left uncut, and serves as a self-hinge or fold line on which a generally trapezoidally-shaped tab is bent perpendicularly outwards from the plane of the strip.
According to the prior invention, each trapezoidal rail tab has a pair of relatively long, laterally opposed outwardly and downwardly sloping edge walls, each joined at the lower end thereof to a short, vertically disposed edge wall of a rectangular pedestal. The lateral spacing between the upper portion of the sloping edge walls of each tab is less than the lateral spacing between the inner facing surfaces of the front and rear airfoil plates, allowing the upper end of the tab to be insertably received in the opening between the front and rear airfoil plates. However, the widths of lower portions of the trapezoid and the pedestal are greater than the lateral spacing between inner walls of the front and rear airfoil plates. Thus, when a turning vane is pushed downwards sufficiently far over an insertably received rail tab, both front and rear airfoil plates are deformed laterally outwards to a flatter contour having a smaller curvature. Wedging action of a rail tab inserted into the space between the front and rear airfoil plates is facilitated by the sloping, wedge-shaped side walls of the rail tab.
According to the prior invention, both front and rear plates are made of a thin, flexible but reasonably stiff material such as sheet steel, which possesses a substantial degree of elasticity when bowed. This elasticity produces a negative hoop tension on both plates, i.e., a force directed radially inwards towards the center of curvature of the plates, which causes both plates to attempt to assume the larger curvatures which they had prior to being deformed by the wedging action of a rail tab. These hoop tension forces cause those portions of the front inner airfoil plate surfaces in contact with the tab side walls to exert a radially inwardly directed gripping force on the tab side walls. The hoop tension forces on the tab side walls also have rearwardly directed force components which force the rear face of tab into abutting contact with the front convex face of the rear airfoil plate. These forces combine to tightly grip the tab, thereby securing the vane to the tab.
In a particular embodiment of the prior invention, the air turning vane included a bowed front airfoil plate having a convex front surface and a bowed rear airfoil plate having a concave rear surface. The rear plate has formed therein a pair of longitudinally spaced apart, generally hemispherically shaped locking buttons which protrude forward from the front or inner convex surface of the rear plate. The two locking buttons are located longitudinally inwards from the upper and lower transverse edge walls of the rear airfoil plate, respectively. Also, the locking buttons are located on the longitudinal center line of the rear airfoil plate, and protrude forwards towards the longitudinal center line of the front airfoil plate.
In embodiments of the invention employing locking buttons, a small rectangular aperture is provided through the thickness dimension of each trapezoidally-shaped tab, above the fold line, for receiving a locking button of a vane. These button-receiving apertures are most conveniently formed in rail sheet stock prior to bending up the tab.
While a vane provided with buttons is being pushed down on a tab inserted between the front and rear vane plates, the lower button protruding inwards from the rear airfoil plate is forced against a vertical wall surface of the rail tab. When the button encounters the aperture formed through the tab near its base, the hoop spring tension in the front and rear airfoil plates, which tends to restore both plates to the initial greater curvature possessed before being wedged laterally outwards by the rail tab, causes the lower button to snap into the aperture in the rail tab. Engagement of an upper transversely disposed lip on the button with the rail tab perforation edge wall securely locks the lower end of the vane to the lower rail.
After a vane has been thus installed on each upstanding tab of a lower rail, an identical upper rail, turned upside down so that its tabs protrude downwards, may be attached to the upper ends of each upstanding vane by aligning the tabs downwardly protruding from the upper rail with corresponding upper openings in the vanes, and pushing downwards on the upper rail to wedgingly engage each vane by an upper tab. Engagement of a lower flat, transversely disposed lip on the upper vane button with the rail tab perforation edge wall securely locks the upper end of the vane to the upper rail. Notably, vane and rail assemblies according to the prior invention, as described above, may be assembled on a job site from pre-manufactured vanes and rails by hand pressure alone, without requiring any tools.
According to the present invention, a method and apparatus for forming locking buttons in vanes of the type described above includes cutting an elongated length of double airfoil vane stock into air turning vanes of a selected length, while simultaneously forming a locking button longitudinally inward from each of the two opposed severed transverse edges of the vane stock. The apparatus according to the present invention includes a guillotine-like shearing structure including front and rear parallel and longitudinally spaced apart blade support plates which vertically slidably support a guillotine blade therebetween. Each blade support plate has through its thickness dimension a crescent-shaped or smile-shaped aperture, having a lower concave wall surface adapted to slidingly receive the front or lower convex surface of a length of double airfoil air turning vane stock inserted through the aperture. Each aperture also has an upper, downwardly convex wall surface adapted to slidingly receive the upper or rear concave surface of the length of air turning vane stock inserted through the apertures. The upper edge wall of each blade support plate has formed therein a centrally located rectangular punch access slot which extends downwardly and penetrates the upper convex aperture wall.
The shear blade of the apparatus according to the present invention includes a plate of generally uniform thickness. The plate in front plan view has a laterally elongated, rectangularly-shaped upper portion, and a downwardly depending triangularly-shaped portion. The latter is symmetrically located with respect to a longitudinal medial plane of the blade, with the apex of the triangle lying on the longitudinal center line of the blade and forming a piercing wedge for severing both front and rear plates of vane stock insertably received through the blade support apertures.
According to the present invention, both the front and rear surface of the upper rectangular portion of the blade have protruding outwards therefrom a separate lancing punch adapted to form generally hemispherically-shaped button-like protuberances in the upper, concave rear edge walls of both sides of a length of vane stock sheared apart by downward motion of the shear blade. Each lancing punch has in front plan view a radiused, downwardly protruding wedge-shaped point symmetrically located on the longitudinal center line of the shear blade. In side elevation view, the downwardly depending point of the lancing punch has a flat outer surface, and a front face which slopes upwardly and inwardly from the outer face to the base of the lancing punch, which is in flat contact with the shear blade face. The front or lower face of the lancing punch is arcuately curved, conformally with the outer point face of the lancing punch.
According to the method of the present invention, the shear blade is elevated to a position above the apertures through the blade slide support plates, and a length of double airfoil vane stock inserted through the rear smile-shaped blade support aperture and extended through the front smile-shaped aperture to a distance from the front surface of the blade equal to the desired length of an air turning vane. The shear blade is then forced sharply downwards, by means of a pneumatic or hydraulic actuator cylinder, for example. As the blade travels downwards, the triangular-shaped piercing point of the blade pierces and severs the forward protruding length of the stock from the rear portion of the stock. Near the downward limit of the shear blade travel, the two lancing punches on the front and rear sides, respectively, of the shear blade, forcibly contact the severed front and rear lengths of the upper concave plate of the vane stock, a short distance forward and rearward, respectively, of the two severed edges. The forcible contact of each lancing punch forms a small transversely disposed slit in the concavely curved rear or upper airfoil plate of the vane stock, and also forms a generally hemispherically-shaped button-like protuberance between the slit and the transverse severed edge of the vane stock. The protuberance, which serves as a locking button as described above, protrudes downwards toward the convexly curved front or lower airfoil plate of the vanes.